Our long-term goal is to understand the host pathogenesis and the pharmacology of herpes simplex virus type 1 (HSV-1) latency and reactivation in order to develop therapeutic strategies to block neuronal HSV-1 reactivation and prevent the corneal scarring that results from recurrent disease. At present, no drug can block HSV reactivation in humans. Clinical observation and experimental models have shown that HSV reactivation is stress mediated. To study latency and reactivation, genetically engineered HSV-1 mutants that are altered in a specific region involved in the transcription of unique RNAs called latency associated transcripts (LAT) will be used, in particular constructs with site-directed mutations in an 800-bp segment of the LAT transcript that is essential for in vivo reactivation. To determine host and viral factors regulating HSV reactivation, three specific aims are proposed: IA) Identify, by microarray analysis, host mRNAs that are upregulated during HSV reactivation in latent mouse trigeminal ganglia (TG) induced by hyperthermic stress or immunosuppression; 1B) Identify specific host cellular mRNAs that are upregulated in specific subpopulations of neurons harboring latent HSV using laser capture microdissection of neurons latent for HSV-1 constructs expressing green fluorescent protein, followed by microarray analysis: 2) Determine specific setsof viral transcripts induced in latent TG relative to the LAT genotype and reactivation phenotype of the infecting HSV-1 constructs; 3) Determine whether propranolol, which is known to block HSV induced reactivation in mice, will selectively inhibit cellular and/or viral mRNAs induced in the TG of heat-stressed mice. Other potential specific inhibitors of host and/or viral transcription upregulation, such as cdk inhibitors and COX-2 will also be tested. Taken together, the results of these studies will permit the identification of viral and host transcripts that are critical in the transition from latency to reactivation. Information generated with and without inhibitors will allow us to identify the key host and viral components that are critical in blocking neuronal reactivation of HSV and preventing recurrent disease. The development of new therapies that prevent the corneal scarring caused by repeated episodes of herpetic disease would represent an important advance protecting vision and decreasing the need for corneal transplantation.